This invention relates to an improved construction of an ejector utilizing a vortex flow for pumping fluids. The ejector of the invention is particularly suitable for pumping fluids at extremely low pressures to ambient pressure.
U.S. patent application Ser. No. 898,961 (a continuation of Ser. No. 653,931) discloses a method and apparatus for pumping a fluid. The apparatus includes a fluid vortex forming chamber having a funnel shaped surface circumscribing a longitudinal axis and converging toward the longitudinal axis from a wide end to a narrow end. The narrow end of the funnel shaped surface communicates with a venturi-like throat which also circumscribes the longitudinal axis.
A driver fluid is introduced tangentially into the wide end of the chamber through a single inlet. The funnel shaped surface and venturi throat are designed to guide the driver fluid toward the throat in the form of a vortex flow having a low pressure region at the eye thereof. A low pressure fluid inlet communicates with the low pressure region of the vortex flow so that the vortex flow draws the low pressure fluid through the inlet and mixes the low pressure fluid with the driver fluid to form a swirling flow of mixed fluid which advances through the venturi-like throat.
The swirling fluid flow which exists the venturi throat swirls into a diffuser formed by spaced apart diverging surfaces which form a conical surface of increasing radius. The diffuser guides the swirling flow along a path of increasing radius to compress the mixed fluids to the ambient pressure at the diffuser outlet while blocking flow of fluid at the ambient pressure of the diffuser outlet to the throat.
As brought in the aforesaid specification the apparatus disclosed therein is capable of forming the driver fluid into a vortex flow which generates extremely low pressures at the eye thereof. Specifically, the apparatus has been found to generate pressures on the order of 100 torr (atmospheric pressure being on the order of 760 torr) at the eye of the vortex.
The present invention provides an ejector which improves the pumping action of an ejector such as disclosed in U.S. patent application Ser. No. 898,961. Specifically, the present invention provides an ejector which is capable of generating pressures at the vortex eye as low as 15 torr using an incompressible driver fluid (such as water, and pressures as low as 21 torr using a compressible driver fluid such as nitrogen. An ejector constructed according to the invention and using nitrogen as a driver fluid is particularly suitable for pumping neon lazer exhaust which is of extremely low pressures.
According to the present invention the driver fluid is introduce tangentially into the wide end of the vortex chamber through a pair of diametrically opposed fluid inlets. With a single inlet, such as disclosed in application Ser. No. 898,961, a separation bubble may eventally form along radially innermost surface of the diffuser member. Unless the diffuser member is skewed slightly with respect to the longitudinal axis, the separation bubble may propagate out to the diffuser outlet, where fluid at the ambient pressure of the diffuser outlet will be drawn into the vortex forming chamber. This would ultimately destroy the low pressure pumping capability of the device. The diametrically opposed driver fluid inlets of the present invention eliminates the possibility of a separation bubble forming along the conical diffuser and propagating outwardly along the diffuser to the outlet, without skewing part of the diffuser relative to the longitudinal axis.
Further according to the invention, a deflector member is provided in the vortex forming chamber. The deflector is disposed along the longitudinal axis and is further disposed radially inward of the venturi throat. The deflector includes a surface diverging away from the longitudinal axis and generally outwardly toward the venturi throat. The diverging surface guides the secondary fluid along a path of increasing radius in the vortex section and increases the mixing of the primary and secondary fluids. This has been found to further improve the pumping efficiency of an ejector utilizing a vortex flow.
Still further according to a particular aspect of the invention, a special vortex forming chamber is provided for pumping low pressure fluids with a compressible driver fluid such as nitrogen. The vortex forming chamber includes a conical surface converging inwardly from the wide end of the chamber to the mouth of the secondary fluid inlet. A pair of guide walls are further provided to guide flow from each driver fluid inlet along the conical surface and forwardly and radially inwardly of the diametrically opposite driver fluid inlet. This construction reduces viscous losses with a compressible driver fluid, and thereby further improves pumping action.
An tornado ejector constructed according to the present invention is also extremely compact in an axial direction and this makes it very advantageous from a size point of view.